Internet of Things is still in the ascendant, and M2M (Machine to Machine) communication attracts more and more attentions in the communication industry. It is predictable that, various industries, such as intelligent water and electricity meter, intelligent logistic tracking, wearable device, vehicles internet, intelligent industrial control, will apply the Internet of Things technique to accomplish corresponding industrial upgrades. Given this, in the future, amount of Internet of Things terminals will far surpass that of H2H (Human to Human) communication terminals, which may reach ten billions or even hundreds of billions. In addition, a quite amount of Internet of Things applications possesses properties, such as small in data volume, insensitive to transmission delay, a relatively long transmission cycle. These properties provide a possibility of developing low-cost Internet of Things terminals. Further, low-cost of the terminals will facilitate popularization of the Internet of Things.
In practical applications of the Internet of Things in some regions, it has been found that, in some application scenarios of the Internet of Things, such as the intelligent water and electricity meter, the intelligent wireless sensor in a basement, terminal signals are affected by an installation position or blocking of buildings, and attenuate greatly. Accordingly, coverage-enhancing technology is applied to improve network coverage without increasing investment of operators, so as to meet requirements of network coverage in the above recited scenarios. Currently, a target demand value of a typical coverage enhancement provided by the operators is 15-20 dB.
In order to meet above recited requirements, 3GPP (3rd Generation Partnership Project) provides a solution for low-cost Internet of Things terminals and coverage enhancements. The low-cost Internet of Things terminals are realized mainly by ways, for example, reducing terminal working band width, decreasing number of terminal radio frequency receiving link channels, reducing terminal peak rate, reducing terminal processing complexity, etc. Further, the coverage enhancement can be realized by ways, such as signal or channel repeating, frequency hopping, transmittal power improvement. In the 3GPP RELEASE 13, NB-IOT (Narrow Band Internet of Things) project sets a goal of designing a NB-IOT terminal only supporting a RF (Radio Frequency) band width of 180 KHz, wherein the NB-IOT terminal is not only able to work on an independent carrier wave (e.g., a carrier wave reusing existing GSM 200 KHz band width), but also able to work inside a band width of a LTE (Long Term Evolution) system.
Band width of the NB-IOT terminal is narrow, and the band width of 180 KHz only corresponds to one PRB (Physical Resource Block) of an existing LTE system, thus, if a reference signal (e.g., C-RS or UE-RS) of the existing LTE system is applied, under the scenario of coverage enhancing, a channel estimation performance may be seriously insufficient, which may cause low efficiency of the system. Moreover, when implementing a RRM (Radio Resource Management) measurement (e.g., RSRP measurement) based on existing reference signals in one PRB, an accuracy of the RRM measurement may be seriously insufficient, thus under the scenario of coverage enhancing, it will be almost impossible to obtain a measurement result meeting measurement accuracy requirements in some working range, such as a working range about −20 dB.